Black rays, hybrdization, and locations. P14, BD, leos, henleii

[Nic]

 

[andersp90]

He he he. Its funny to watch these threads.

Facts being thrown all over and crazy theories being made.

Just like the "is cooked foods ok"? Sure, didn’t take more than 5 sek before someone said they where useless. Oh, really I thought?

Hmmmmm. That was strange. Cos i had a friend who had analyzed the nutrition levels in cooked shrimps (its part of his job). And it was only 1-2 % lower compared to raw ones!
And it was funny how silent the thread became!

So the claims being made was pure theory being pulled out of thin air!

So, before this thread becomes a balloon of hot air, let’s stick to the facts. And turn it all around!


Facts about the fish being discussed.


Potamotryon leopoldi:

Black, with white spots. These spots can very in size, colour and shape.

They grow to about 80 cm.

Potamotrygon henlei:

These fish can range in colour from a light brown to black/gray. The spots can vary in size and shape. But often white with a black ring around. This fish also have white spots on the belly and disc edge.

They also get 80 cm.

Potamotrygon sp. (P14):

These can also range a lot, some having a faint brown colour. But most are black.
Their spots are often white and small, though they can range in size and numbers.

Their max is in the 60-70 cm range.

Potamotrygon sp. “Pearl”:

These fish can range in colour from almost white to a very dark brown.
The “Pearls” are rings of a lighter colour with the ground colour in the middle, though this can vary a lot. The pearls change throughout their lives.

They get to around 60-70 cm.


So, most people reading these descriptions would probably say that this sounds like different unique species. And I think we can all agree that they are easy to tell apart.
And this leads to the big question I have for you.

If these 4 “species” really cross bred all the time, just how would they be able to evolve to become so unique looking?

Now, I am not saying that it never happens. But if ever, very rarely.

About the BD/Sao felix rays, im not sure what to think. New WC shots make me think to much. Some look like thousand islands, and some “normal” BD´s. Its to early to say anything for sure.

So, read this, think, and then answer.

 

[rayman]

Hi Anders,

where do you get the max. size? True measurements?
The largest sp. Itaituba (P14) I've seen had only 52-55 cm diameter (picture with ruler from scientific work at the Tapajos and one specimen a friend of mine has in his tank).

Another thing is that from coloration you can not differentiate some species properly, like leopoldi and henlei. The main differenz in this two species is the dentition. So any discussion based on coloration is worthless.

btw. the rule that leos have no spots at the edge of the disk and the ventral surface is based on only two specimen from two locations at the Xingu (the holotype and one additional specimen). We know now that there are some variants in coloration at other finding places and tributaries of the Xingu. Scientific work was done at Sao Felix do Xingu and some of the examined specimen had spots at the disk edge and at the ventral. These rays had white spots, open rings and lines at the dorsal and these were leopoldi too. So what is the reason for us to discuss this from far away if scientist find out that these are leopoldi?

 

[andersp90]

Hi Anders,

where do you get the max. size? True measurements?
The largest sp. Itaituba (P14) I've seen had only 52-55 cm diameter (picture with ruler from scientific work at the Tapajos and one specimen a friend of mine has in his tank).

Another thing is that from coloration you can not differentiate some species properly, like leopoldi and henlei. The main differenz in this two species is the dentition. So any discussion based on coloration is worthless.

btw. the rule that leos have no spots at the edge of the disk and the ventral surface is based on only two specimen from two locations at the Xingu (the holotype and one additional specimen). We know now that there are some variants in coloration at other finding places and tributaries of the Xingu. Scientific work was done at Sao Felix do Xingu and some of the examined specimen had spots at the disk edge and at the ventral. These rays had white spots, open rings and lines at the dorsal and these were leopoldi too. So what is the reason for us to discuss this from far away if scientist find out that these are leopoldi?

Hello rayman.

No, i have never seen a P14 bigger than 60 cm.

But the max limited is being pushed all the time. So better set it a little higher. Just look a the scobina. some say 30 is the max. But i have seen a 37 cm girl. And still growing a bit (well she was ).

I am also aware of the fact that some leos have spots on the disc edge.
These above descriptions are only ment as a general guide to each "species".

As for the Sao felix Black Diamonds, i myself believe they are Potamorygon Leopoldi. But very nice ones.

though, I have never seen a Leopoldi with dark rings around their spots. So I think its a vaild way of telling leopoldi and henlei apart.

 

[DB junkie]

You have to have "hot air" in a conversation. Without this, those of us without scientific degrees, who are NOT biologists, take something away from the conversation. We are all here to learn. No questions are stupid questions. It only takes a wrong turn when people start basing fact on assumptions. And a lot of what is known about FW rays is assumption. Thread like these are discusions, NOT who's right and who's wrong. It's kinda difficult for people to stay interested in a subject like this if they are shunned for simply trying to participate in the conversation.

 

[reefman]

very interesting thread

 

[Miles]

Miles, your maps are flawed. The second one just shows the far western point of the Amazon, far from the XIngu and Tocantins. The rivers are not flooding as you say they are. Plus Brazil isnt exactly the largest country in the world.

I said the second map is near Manuas where the Madeira and Negro fork.. I was just using it as an example to show how vastly flooded the basins of these river systems can become, in which migratory travel becomes more accessible.

Hmm I thought Brazil was the largest but your right it's the 5th largest.. maybe if I keep saying it's the largest, it will become fact Largest in S.A. is what I ment, I promise

Also look at other species. Lets take the genus Geophagus. These guys can breed with each other but they arent. Species found in the Xingu are NOT found and breeding with species found in the Tocantins.

I would imagine that Cichlids, being the more evolved species, with more specific instinctive parental care/breeding behavior would be more selective in the breeding process. Having a shorter gestation period, with larger amounts of offsprings, and mating rituals that might be specific to a type of variant.

I believe stingrays have a much different selection method when it comes to breeding - Like "Wow I came across a female that is viable, lets bang it.".. when Cichlids would be more - Like "Wow I came across a few dozen females, let's see who dances purdy the best." ..

Do some research on the Xingu and Tocantins. They flow into deep gorges and through water falls that flood waters would NEVER go over.

Do these areas have seasonal flooding? I was watching a show on Malawai the other day and they had these massive niagra type water falls, but they said they were completely submersed during the wet season..

Also, what do you think of the hydroelectric dams being built? Patricia Charvet-Almeida mentioned the issue of isolating species behind these dams, which would show me that migration was part of their normal behavior before-hand.

I'm not saying its impossible. My argument that in recent times (again on the geologic scale) the Xingu and the Tocantins and the species found in each river, have been very isolated from one another. Of course at one point in time these rays all had a common ancestor so maybe that is why we are see traits that could lead us to believe in hybrids.

.. but .. I think that hybridization is much more likely on the short-term, as evoluationary descendants would have to be partitioned from one another to develop specific traits over the long term.. (tail structure, etc)

So in other words - I would say that things like Reticulata vs. Tiger vs. Motoro would be long-term evolutionary cousins (sorry for the bad terminology).. but species like Leopoldi vs. Henlei vs. P14 would be more-so short-term hybrids.

Also we can not compare this to human breeding! lol. Asians, Hispanics, Whites, blacks, ect are all ONE species. Its more like Homo sapiens breeding with neanderthals, lol maybe we could even argue that isnt even a good enough comparison as neanderthals are now considered a sub-species of H.sapiens...weird huh.

Potamotrygon are all ONE species, too.. right? Now.. if they discovered that, for example, reticulata could not produce viable offspring with other types of potamotrygon, it would probably become a new subspecies. But until now, I look at it alot like the human race.. Different sizes, tones, shapes, but they are all able to interbreed and produce viable offspring.



One thing that is interesting is how we look at max sizes.. if we used our reasoning on humans.. all humans would get a max size 7 feet tall, and we will all eventually need to upgrade to SUVs and taller doorways.

 

[JD7.62]

I said the second map is near Manuas where the Madeira and Negro fork.. I was just using it as an example to show how vastly flooded the basins of these river systems can become, in which migratory travel becomes more accessible.

Hmm I thought Brazil was the largest but your right it's the 5th largest.. maybe if I keep saying it's the largest, it will become fact Largest in S.A. is what I ment, I promise

Im sure that is what you meant, I was just pointing out that the flooding there doesnt represent the flooding of the Xingu.

I would imagine that Cichlids, being the more evolved species, with more specific instinctive parental care/breeding behavior would be more selective in the breeding process. Having a shorter gestation period, with larger amounts of offsprings, and mating rituals that might be specific to a type of variant.

I believe stingrays have a much different selection method when it comes to breeding - Like "Wow I came across a female that is viable, lets bang it.".. when Cichlids would be more - Like "Wow I came across a few dozen females, let's see who dances purdy the best." ..

Possibly, but we all know cichlids will meet with other species easily too.

Do these areas have seasonal flooding? I was watching a show on Malawai the other day and they had these massive niagra type water falls, but they said they were completely submersed during the wet season..

Im not 100% on how the gorges and rapids are changed during flooding. Like I said before, it more then chance that these two rivers are both rather isolated and both have rather unique fish.

Also, what do you think of the hydroelectric dams being built? Patricia Charvet-Almeida mentioned the issue of isolating species behind these dams, which would show me that migration was part of their normal behavior before-hand.

I have come to interpret that the dams didnt stop migration of the fish, rather the lakes formed behind the dam allow for more viable habitat for the rays and therfor their numbers increased.

.. but .. I think that hybridization is much more likely on the short-term, as evoluationary descendants would have to be partitioned from one another to develop specific traits over the long term.. (tail structure, etc)

So in other words - I would say that things like Reticulata vs. Tiger vs. Motoro would be long-term evolutionary cousins (sorry for the bad terminology).. but species like Leopoldi vs. Henlei vs. P14 would be more-so short-term hybrids.

Who knows? I think only DNA testing could prove that. We cant go by outside traits alone. Everything else is just speculation.

Potamotrygon are all ONE species, too.. right? Now.. if they discovered that, for example, reticulata could not produce viable offspring with other types of potamotrygon, it would probably become a new subspecies. But until now, I look at it alot like the human race.. Different sizes, tones, shapes, but they are all able to interbreed and produce viable offspring.



This is what I find odd. The genus Potamotrygon challenges the very definition of "species."

Is any one aware of any other elasmos genus' with sp that can inter breed?

One thing that is interesting is how we look at max sizes.. if we used our reasoning on humans.. all humans would get a max size 7 feet tall, and we will all eventually need to upgrade to SUVs and taller doorways.

...

 

[Rayfan]

Hybrid and crossing do not happen easily in wild nature. This is because if there are males and females of the same breed, they would always mate with the same breed. In captivity, the rays are forced to be kept in the same tank/ pond with only the different breed, thus crossing happened.

 

[DB junkie]

^ So if this is true you should be able to throw in a pair of pearls, a pair of Leos, and a pair of Marbles together in one pond and NO crossbreeding will happen ..... Correct????